def dz(n):
    s = 1
    if n % 2 == 1:
        for i in range(1, n+1, 2):
            s *= i
    else:
        for i in range(2, n+1, 2):
            s *= i

    return s


def main():
    while True:
        try:
            n = int(input())
            print(dz(n))
        except:
            break


if __name__ == '__main__':
    main()
